Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles
  • G03G9/09—Colouring agents for toner particles
  • G03G9/0906—Organic dyes
  • G03G9/092—Quinacridones

Definitions

• the present invention relates to an improved magenta colorant for multi-color electrophotographic recording processes, the magenta colorant being a mixed crystal of 2,9-dimethylquinacridone and unsubstituted quinacridone in a specific mixing ratio.
• the toner is the component containing the colorant, which gives color in the recording process
• its triboelectric chargeability is indispensable, the sign and the amount of the chargeability being of fundamental importance.
• the present invention was based on the need to find a magenta colorant which improves the triboelectric chargeability of the toner and at the same time has the required color shade and transparency.
• a "latent charge image” is generated on a photoconductor drum. This is achieved by charging the photoconductor drum with a corona discharge and then imagewise exposing the electrostatic charged surface of the photoconductor drum, the exposure of the charge to the grounded base at the exposed locations being effected by the exposure. The "latent charge image” thus generated is then developed by applying a toner.
• the toner is transferred from the photoconductor drum to, for example, paper, textiles, foils or plastic and is fixed there, for example by pressure, radiation, heat or the action of solvents.
• the photoconductor used is then cleaned and is available for a new recording process.
• Electrophotographic multi-color reproduction can be achieved, for example, by three successive recording processes with three toners of the respective primary colors magenta, yellow and cyan.
• a measure of the toner quality is its specific chargeability Q / M (charge per unit mass).
• the color shade of toners for monochrome recordings is essentially determined from an aesthetic point of view; transparency and color location are decisive for multi-pass reproduction based on the principle of "subtractive color mixing".
• mixtures of pigments have proven to be suitable for setting the desired shade (JA-OS 59/219756, JA-OS 59/220750).
• pigment mixtures Compared to systems with only 1 pigment component, pigment mixtures have the disadvantage that they are cloudy and show a lower transparency. It also results in the application
• the disadvantage of pigment mixtures is that the already complex toner formulations have to be expanded by at least 1 component, which in turn means that pigment compatibility, mixing problems and deviating color shades have to be taken into account.
• a toner composition color-coordinated by a pigment mixture also has the required triboelectric chargeability, so that a charge control agent, which in turn is usually colored itself, must also be added, which again raises problems of the deviating color shade or incompatibilities leads.
• the chargeability of the toner is described in US Pat. No. 4,057,426, using a complex carrier consisting of polymer-coated steel particles, the polymer in turn containing a certain proportion of copper tetra-4- (octadecylsulfonamido) phthalocyanine needs to be improved.
• magenta toners which contain 2,9-dimethylquinacridone as colorants
• a "nickel berry” carrier nickel particles with a special knot-shaped surface
• US Pat. Nos. 3,909,259 and 3,804,619 a special combination of carrier and toner could ensure perfect toner transfer. Since no uniform carrier is available for the three toner colors due to the use of a special nickel carrier for the magenta toner, the recording process becomes more complex, especially since the use of nickel is inherently problematic because of its toxicological concern.
• magenta toners Another approach to improving the poor chargeability of magenta toners is to optimize the resin in terms of its tribolelectric properties as described in DE-OS 2 447 083.
• a resin optimized in this way for its triboelectric properties now often shows problems, for example with regard to its fixing and offset behavior, its glass point and its dispersibility.
• the three color toners or developers in the multi-color copying machine do not differ in terms of pigments, but also in terms of toner binders.
• the aim is that in a multi-color copier the respective components for toner and carrier or developer are as uniform as possible and differ only in terms of the colorants used for yellow, cyan and magenta.
• the present invention has surprisingly shown that it is possible to give the toner a significantly improved triboelectric chargeability by means of suitable mixed crystals of 2,9-dimethylquinacridone and unsubstituted quinacridone without significantly changing the color shade of the 2,9-dimethylquinacridone.
• the chargeability thus improves from -23.0 ⁇ C / g (toner example 4, with 2,9-dimethylquinacridone) to up to -40.5 ⁇ / g (toner example 3, mixed crystal 3 parts of 2,9-dimethylquinacridone, 1 Part of unsubstituted quinacridone).
• toners with mixed crystals of 2,9-dimethylquinacridone and unsubstituted quinacridone show a similarly good charge profile as those with 2,9-dimethylquinacridone alone.
• the color shade of the toner colored with the colorant (mixed crystal) according to the invention corresponds to the color shade of toners with 2,9-dimethylquinacridone known to be suitable.
• a mere pigment mixture of 2,9-dimethylquinacridone and quinacridone in a ratio of, for example, 3: 1, incorporated into the toner does not give the required shade and transparency.
• magenta toners with the colorants (mixed crystals) used according to the invention have the necessary transparency.
• the triboelectric chargeability of mixed crystals of the same composition can vary, for example, between -31.1 ⁇ / g (toner example 1) and -40.5 ⁇ C / g (toner example 4).
• the present invention thus relates to improved magenta colorants for electrophotographic multi-color recording processes consisting of mixed crystals with 95 to 60 parts of a compound of the formula I below and 5 to 40 parts of a compound of the formula II below the use thereof for the production of toners which are used for electrophotographic copying or duplication of originals and for the printing of electronically, optically or magnetically stored information, and the use of toners or developers which have been produced using the abovementioned magenta colorants for magenta reproduction in multi-color electrophotographic recording.
• the preparation of the mixed crystal pigments mentioned is possible in a manner known per se, for example by jointly redissolving the mixed crystal components from sulfuric acid or another suitable solvent and subsequent solvent treatment, as described in US Pat. No. 3,160,510, or by salt grinding the mixed crystal components and subsequent solvent treatment ( DE-AS 1 217 333) or by cyclizing the correspondingly substituted diamino-terephthalic acid mixtures and subsequent solvent treatment, as indicated, for example, in DE-AS 1 217 333.
• either dried and ground pigment or, for example, an aqueous pigment dispersion or a pigment press cake can be used to incorporate the mixed crystal into the toner binder.
• the amount of electrostatic charging of the toner using mixed crystals of compounds of the above formulas (I) and (II) in the specified mixing ratio or on the comparison system with C.I. Pigment Red 122 (formula (I)) was measured on standard systems under the same conditions (such as the same dispersion times, same particle size distribution, same particle shape) at 23 ° C. and 50% relative atmospheric humidity.
• the toner is activated in a two-component developer by swirling the toner with a carrier (3 parts toner to 97 parts carrier) for 30 minutes on a roller bench (150 revolutions per minute).
• the particle size distribution of the sighted toner powder was determined using a Cilas 715 granulator from Cilas.
• the average particle sizes for the toners listed in the examples were between 7.4 ⁇ m and 7.9 ⁇ m.
• the mixed crystal pigments A, B and C are mixed crystals of 3 parts of the compound of the formula I and 1 part of the compound of the formula II mentioned, for the preparation of mixed crystal A (cf. Example 1) the hydrolysis from polyphosphoric acid was carried out in an aqueous medium at 50 ° C. and an aftertreatment in alcoholic solvent was carried out at 125 ° C. for 5 hours; of mixed crystal B (cf. Example 2) the hydrolysis from polyphosphoric acid was carried out in an aqueous medium at 50 ° C. and an aftertreatment in alcoholic solvent was carried out at 150 ° C. for 5 hours; of mixed crystal C (cf. Example 3), the hydrolysis from polyphosphoric acid was carried out in an aqueous medium at 70 ° C. and an aftertreatment in alcoholic solvent was carried out at 120 ° C. for 5 hours.
• the mixed crystals labeled A, B and C are characterized by three strong lines at 16.21; 8.43 and 3.28 ⁇ , two moderate lines at 8.06 and 3.51 ⁇ and other weak lines in the X-ray diffraction spectrum.
• the 2,9-dimethylquinacridone listed in Comparative Example 4 is the CI Pigment Red 122 (®Hostaperm-Rosa E).
• the desired particle fraction was activated with a carrier composed of magnetite particles of size 50 to 200 ⁇ m of the type 90 ⁇ m Xerographic Carrier from Plasma Materials Inc., coated with styrene methacrylate 90:10.
• the measurement is carried out on a standard Q / M measuring stand [cf. J.H. Dessauer, H.E. Clark “Xerography and related Processes", Focal Press, N.Y. 1965, page 289]; by using a sieve with a mesh size of 25 ⁇ m (508 mesh per inch), from Gebrüder Kufferath, Düren, it was ensured that no carrier could be entrained in the toner blowouts.
• the Q / M value was determined to be -31.1 ⁇ C / g.
• the Q / M value was determined to be -36.8 ⁇ C / g.
• the Q / M value was determined to be -40.5 ⁇ C / g.
• the Q / M value was determined to be -23.0 ⁇ C / g.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Developing Agents For Electrophotography (AREA)
• Photoreceptors In Electrophotography (AREA)

Applications Claiming Priority (2)

Publications (3)

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Family Applications (1)

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• 1986
  • 1986-05-30 DE DE19863618214 patent/DE3618214A1/de not_active Withdrawn
• 1987
  • 1987-05-26 EP EP87107650A patent/EP0247576B1/de not_active Expired - Lifetime
  • 1987-05-26 DE DE8787107650T patent/DE3783654D1/de not_active Expired - Lifetime
  • 1987-05-27 JP JP62128508A patent/JP2610618B2/ja not_active Expired - Lifetime
  • 1987-05-28 US US07/055,347 patent/US4777105A/en not_active Expired - Lifetime

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